The fifth national Armed Forces Day will begin today with an artillery regiment firing a volley of gun blasts at Nottingham Castle.
Further celebrations are planned across the UK.
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David Cameron has raised concerns after figures showed 100 babies spent time living behind bars last year.
About 124,000 patients had to wait for at least 12 hours in accident and emergency departments last year, according to an investigation.
Today's rain will clear into the North Sea tonight, but winds will stay strong, with showers feeding in to the north and west.